Extração e caracterização de hidrocoloide obtido das cascas da pitaya-vermelha (Hylocereus polyrhizus) e branca (Hylocereus undatus)

Abstract

The Cactaceae family stands out for its potential use in the extraction of hydrocolloids, in which dragon fruit species are included. These hydrocolloids have potential stabilizing, gelling, emulsifying, and other functions. In this way, this work aimed to extract hydrocolloids from the peel of red (HV) and white pitayas (HB) and determine the physicochemical and morphological characteristics to obtain a technologically quality hydrocolloid. Preliminary extraction tests were conducted, including hydration in water and precipitation in ethanol. Subsequently, drying kinetics were performed in a circulating air oven at temperatures of 50 and 60 ºC. Five mathematical models were applied to fit the experimental data, with the best drying temperature defined by DPPH and FRAP antioxidant capacity methods. The mucilage obtained at 60 ºC was characterized regarding phenolic compounds, minerals, acids and sugars profile, color, infrared spectrophotometry (FTIR), degree of methoxylation (GM), and scanning electron microscopy (MEV). Analyzing the results, it was determined that the extraction conditions T2 (room temperature (28 ± 2 °C) with agitation) yielded the best results with a 25% yield, and the Lewis mathematical model best explained the experimental data. The drying temperature of hydrocolloids at 60 °C showed better conditions when correlating antioxidant capacity and drying rate data. The hydrocolloid from the red pitaya peel (HV) obtained higher concentrations of phenolic compounds (11.66 mg Kg 1), while the hydrocolloid from the white pitaya peel (HB) stood out with a higher content of simple sugars, glucose, and fructose (27.30 g 100 g-1). HV and HB hydrocolloids showed no significant difference in mineral profile (15.22 g Kg-1 - HV and 15.80 g Kg 1 - HB) and organic acids (11.07 g 100 g-1 - HV and 11.08 g 100 g-1 - HB). In the color analysis, it was observed that the convective drying process at 60 ºC did not affect the color parameters of HV, while HB experienced a reduction in luminosity (L*), b* coordinate, chromaticity (C*), and hue angle. FTIR spectra confirmed the predominance of high methoxyl pectin in the composition of hydrocolloids, with methoxylation degrees of 73.5% and 61.3% for HV and HB hydrocolloids, respectively. Scanning electron microscopy (MEV) analysis at resolutions of 50 and 100 ¿m for HV and HB hydrocolloids showed similar behaviors, despite being different varieties, with the presence of clusters and porous structures. The hydrocolloids from red and white pitaya peels have viability for obtaining and applying pectin, in addition to presenting bioactive and functional properties for use in the food industry and/or other industrial segments. This contributes to the sustainable development of the region and adds value to pitaya waste.